Enodeb, user equipment and wireless communication method

ABSTRACT

Provided are an eNB, a UE and wireless communication methods. A UE according to an embodiment of the present disclosure can comprise circuitry operative to determine valid transmission time interval(s) (TTI(s)) for a physical channel in a subframe based on the resource element (RE) number of each TTI in the subframe; and a receiver operative to receive the physical channel in one or more of the valid TTI(s) by blindly decoding part or all of the valid TTI(s), wherein each TTI comprises 1-7 orthogonal frequency division multiplexing (OFDM) symbols.

BACKGROUND 1. Technical Field

The present disclosure relates to the field of wireless communication,and in particular, to an eNode B (eNB), a user equipment (UE), andwireless communication methods for transmission time interval (TTI)indication.

2. Description of the Related Art

Latency reduction is one topic in 3GPP, and the main method is to changeTTI length for example from 1 ms to 1 orthogonal frequency divisionmultiplexing (OFDM) symbol, which can largely reduce the transmissionlatency.

SUMMARY

One non-limiting and exemplary embodiment provides an approach todetermine or indicate candidate TTI(s) for a physical channel.

In a first general aspect of the present disclosure, there is provided auser equipment (UE) comprising: circuitry operative to determine validtransmission time interval(s) (TTI(s)) for a physical channel in asubframe based on the resource element (RE) number of each TTI in thesubframe; and a receiver operative to receive the physical channel inone or more of the valid TTI(s) by blindly decoding part or all of thevalid TTI(s), wherein each TTI comprises 1-7 orthogonal frequencydivision multiplexing (OFDM) symbols.

In a second general aspect of the present disclosure, there is providedan eNode B (eNB) comprising: circuitry operative to determine validtransmission time interval(s) (TTI(s)) for a physical channel in asubframe based on the resource element (RE) number of each TTI in thesubframe; and a transmitter operative to transmit the physical channelin one or more of the valid TTI(s) to a user equipment (UE), whereineach TTI comprises 1-7 orthogonal frequency division multiplexing (OFDM)symbols.

In a third general aspect of the present disclosure, there is providedan eNode B (eNB) comprising: circuitry operative to generate a bitmapindicating candidate transmission time interval(s) (TTI(s)) for aphysical channel in a subframe; and a transmitter operative to transmitthe bitmap in the radio resource control (RRC) or medium access control(MAC) layer, and transmit the physical channel in one or more of thecandidate TTI(s), wherein each TTI in the subframe comprises 1-7orthogonal frequency division multiplexing (OFDM) symbols, and the sizeof the bitmap depends on the lengths of TTIs in the subframe.

In a fourth general aspect of the present disclosure, there is provideda user equipment (UE) comprising: a receiver operative to receive abitmap indicating candidate transmission time interval(s) (TTI(s)) for aphysical channel in a subframe in the radio resource control (RRC) ormedium access control (MAC) layer; and circuitry operative to determinethe candidate TTI(s) based on the bitmap, wherein the receiver is alsooperative to receive the physical channel in one or more of thecandidate TTI(s) by blindly decoding the candidate TTI(s), and each TTIin the subframe comprises 1-7 orthogonal frequency division multiplexing(OFDM) symbols, and the size of the bitmap depends on the lengths ofTTIs in the subframe.

In a fifth general aspect of the present disclosure, there is provided awireless communication method performed by a user equipment (UE)comprising: determining valid transmission time interval(s) (TTI(s)) fora physical channel in a subframe based on the resource element (RE)number of each TTI in the subframe; and receiving the physical channelin one or more of the valid TTI(s) by blindly decoding part or all ofthe valid TTI(s), wherein each TTI comprises 1-7 orthogonal frequencydivision multiplexing (OFDM) symbols.

In a sixth general aspect of the present disclosure, there is provided awireless communication method performed by an eNode B (eNB), comprising:determining valid transmission time interval(s) (TTI(s)) for a physicalchannel in a subframe based on the resource element (RE) number of eachTTI in the subframe; and transmitting the physical channel in one ormore of the valid TTI(s) to a user equipment (UE), wherein each TTIcomprises 1-7 orthogonal frequency division multiplexing (OFDM) symbols.

In a seventh general aspect of the present disclosure, there is provideda wireless communication method performed by an eNode B (eNB)comprising: generating a bitmap indicating candidate transmission timeinterval(s) (TTI(s)) for a physical channel in a subframe; transmittingthe bitmap in the radio resource control (RRC) or medium access control(MAC) layer; transmitting the physical channel in one or more of thecandidate TTI(s), wherein each TTI in the subframe comprises 1-7orthogonal frequency division multiplexing (OFDM) symbols, and the sizeof the bitmap depends on the lengths of TTIs in the subframe.

In an eighth general aspect of the present disclosure, there is provideda wireless communication method performed by a user equipment (UE)comprising: receiving a bitmap indicating candidate transmission timeinterval(s) (TTI(s)) for a physical channel in a subframe in the radioresource control (RRC) or medium access control (MAC) layer; determiningthe candidate TTI(s) based on the bitmap; and receiving the physicalchannel in one or more of the candidate TTI(s) by blindly decoding thecandidate TTI(s), wherein each TTI in the subframe comprises 1-7orthogonal frequency division multiplexing (OFDM) symbols, and the sizeof the bitmap depends on the lengths of TTIs in the subframe.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings, in which:

FIG. 1 schematically illustrates some examples of TTI length reduction;

FIG. 2 schematically illustrates candidate TTIs for transmitting EPDCCHin a subframe;

FIG. 3 schematically illustrates a block diagram of an eNB according toan embodiment of the present disclosure;

FIG. 4 illustrates a flowchart of a wireless communication methodperformed by an eNB according to an embodiment of the presentdisclosure;

FIG. 5 schematically illustrates a block diagram of a UE according to anembodiment of the present disclosure;

FIG. 6 illustrates a flowchart of a wireless communication methodperformed by a UE according to an embodiment of the present disclosure;

FIG. 7 schematically illustrates a block diagram of a UE according to anembodiment of the present disclosure;

FIG. 8 schematically illustrates reference signal assumption in anexample;

FIG. 9 illustrates a flowchart of a wireless communication methodperformed by a UE according to an embodiment of the present disclosure;and

FIG. 10 illustrates a flowchart of a wireless communication methodperformed by an eNB according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part thereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. It will be readily understood that the aspects ofthe present disclosure can be arranged, substituted, combined, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated and make part of this disclosure.

Latency reduction is a topic in 3GPP RAN1 and the main method is toreduce TTI length for example from 1 ms to 1-7 OFDM symbols so thattransmission latency can be reduced. FIG. 1 shows some examples of TTIlength reduction. In FIG. 1, from the top to the bottom, the first plotshows normal TTIs, that is, the TTI length is one subframe; the secondplot shows TTIs whose length is 1 slot (7 OFMD symbols); the third plotshows TTIs whose length is 4 or 3 OFDM symbols (for example, the firstand the third TTIs in a subframe have 4 OFDM symbols, and the second andthe fourth TTIs have 3 OFDM symbols); the fourth plot shows TTIs whoselength is 1 OFDM symbol.

Normally, one physical channel such as an EPDCCH or PDSCH is transmittedin one TTI regardless of how long the TTI is. If the TTI length is 1OFDM symbol, the physical channel will be transmitted in 1 OFDM symbol;if the TTI length is 7 OFDM symbols, the physical channel will betransmitted in 7 OFDM symbols. It is noted that TTI is a generalterminology which can be used for any channel transmission. For example,the physical channel herein can refer to any downlink channel such asEPDCCH and PDSCH.

Taking EPDCCH as an example, assuming one shortened TTI whose length issmaller than one subframe transmits one EPDCCH, it is not feasible toassume all TTIs of a subframe are potential to transmit the EPDCCH as itwill largely increase UE's blind decoding (BD) times in the subframe andcause large UE complexity. Therefore, it is proposed that only some TTIsin a subframe are configured to be candidates to transmit the EPDCCH.FIG. 2 schematically illustrates candidate TTIs for transmitting EPDCCHin a subframe, wherein the length of the TTIs is one OFDM symbol. In theexample of FIG. 2, the EPDCCH can only be transmitted in the candidateTTIs, and the UE only needs to blindly decode the candidate TTIs. Insuch a way, the BD times can be reduced.

In order for the above mechanism in which a physical channel is onlytransmitted in candidate TTIs for the physical channel in a subframe towork, the UE should know which TTIs are the candidate TTIs for thephysical channel.

In an embodiment of the present disclosure, a 14 bit bitmap in the radioresource control (RRC) or medium access control (MAC) layer can be usedto indicate the candidate TTIs to each UE. This 14 bit bitmap can beused for all possible TTI lengths. For TTIs with the length of 1 OFDMsymbol, each bit in the 14 bit bitmap indicates whether one TTI is acandidate TTI, for example, bit “1” means candidate, and bit “0” meansnon-candidate. For TTIs with larger length, 2 or more bits can be usedto indicate one TTI's situation, for example, for TTIs with the lengthof 2 OFDM symbols, 2 bits can be used to indicate one TTI's situation.

In the above embodiment, a unified 14 bitmap is used for all possibleTTI lengths, which may cause relatively large overhead. In anotherembodiment, the size of the bitmap to indicate candidate TTIs in asubframe can depend on the lengths of TTIs in the subframe. Based on thelengths of the TTIs, the number of TTIs in a subframe can be calculated,and the bit number of the bitmap can be corresponding to (e.g., equalto) the number of the TTIs.

For example, when the lengths of all the TTIs are the same in asubframe, if the TTI length is 1 OFDM symbol, then the number of TTIs ina normal subframe is 14, and a 14 bit bitmap can be used; if the TTIlength is 7 OFDM symbols, then the number of TTIs in a normal subframeis 2, and a 2 bit bitmap can be used. For special cases, if the TTIlength is not an exact divider of 14 (the number of OFDM symbols of anormal subframe), at least two TTIs in the subframe can be arranged tooverlap each other, or some OFDM symbols (for example, the last m OFDMsymbols, where m is the remainder when 14 is divided by the TTI length)in the subframe can be not assigned to the TTIs. For example, if the TTIlength is 4, then there can be 4 TTIs in the subframe by overlapping thefirst TTI and the second TTI with one OFDM symbol (that is, the endingOFDM symbol of the first TTI is the starting OFDM symbol of the secondTTI) and overlapping the third TTI and the fourth TTI with one OFDMsymbol (that is, the ending OFDM symbol of the third TTI is the startingOFDM symbol of the fourth TTI), and thus a 4 bit bitmap can be used;alternatively, there can be 3 TTIs in the subframe by not assigning thelast two OFDM symbols in the subframe to any TTI, and thus a 3 bitbitmap can be used.

In another example, the lengths of the TTIs can be not all the same in asubframe in order to make full use of the OFDM symbols of the subframe,such as the TTI arrangement shown in the third plot in FIG. 2, in whichthe lengths of the first TTI and the third TTI in the subframes are 4OFDM symbols, and the lengths of the second TTI and the fourth TTI are 3OFDM symbols. In this case, the number of TTIs can be counted based onthe specific TTI arrangement in the subframe. For the example shown inthe third plot in FIG. 2, the number of TTIs in the subframe is 4, and a4 bit bitmap can be used.

Based on the above concept of using different bitmaps for differentsubframes with different TTI lengths or numbers, an embodiment of thepresent disclosure provides an eNB 300 as shown in FIG. 3 whichschematically illustrates a block diagram of the eNB 300 according to anembodiment of the present disclosure. The eNB 300 can comprise circuitry301 operative to generate a bitmap indicating candidate TTI(s) (i.e.,one or more TTIs) for a physical channel in a subframe; and atransmitter 302 operative to transmit the bitmap in the RRC or MAC layerto a UE, and transmit the physical channel in one or more of thecandidate TTI(s) to the UE. Each TTI in the subframe comprises 1-7 OFDMsymbols, and the size of the bitmap depends on the lengths of TTIs inthe subframe. Exemplary ways of determining the size of the bitmap canrefer to the above description on determining the TTI number and thebitmap size.

In the embodiment, the eNB 300 transmits a bitmap whose size depends onthe lengths of TTIs in a subframe in the RRC or MAC layer to a UE forthe UE to determine the candidate TTI(s) in the subframe. Therefore, thebitmap size can be optimized, and the overhead can be reduced. It isnoted that, in the present disclosure, one physical channel (such asEPDCCH and PDSCH) can be transmitted in one or more candidate TTIs. Whenone physical channel is transmitted in multiple TTIs, the UE can jointlydecode the multiple TTIs carrying the physical channel.

In an embodiment, the lengths of the TTIs in the subframe can beUE-specific, in other words, not all UEs are configured by the same TTIlength. As an example, the lengths of the TTIs in the subframe depend onUE's coverage situation. For example, for a cell-edge UE whose radiocondition is relatively bad, it is reasonable to configure more OFDMsymbols as the TTI length since the channel estimation performance willbe relatively bad; for a cell-center UE who has relatively good radiocondition, it is reasonable to configure shorter TTI length (forexample, 1 OFDM symbol) since the channel estimation performance will berelatively good. The eNB can judge UE's coverage situation from areceived uplink signal or the Reference Signal Received Power (RSRP)report.

In an embodiment of eNB 300, the special or partial subframes can usethe same bitmap as the normal subframes. Herein, the “special subframe”is as defined in the specification 3GPP TS 36.211 concerning TDD, andthe “partial subframe” is a subframe where the transmission starts inthe 2^(nd) slot of the subframe as defined in the specification 3GPP TS36.211 concerning unlicensed carrier access. The bitmap size for thenormal subframes can be determined as described in the above. If thesubframe is a special or partial subframe, n bits (for example, thefirst n bits) of the bitmap are applied to indicate the candidateTTI(s), and n depends on the number of TTIs in the special or partialsubframe. For example, in the case of special subframe configuration 0whose symbol number of DwPTS is 3, if the TTI length is 4 OFDM symbols,the bitmap of “1100” can mean that the first and second TTIs of thespecial subframe and the normal subframe are candidate TTIs.Alternatively, a special bitmap can be used to indicate which TTI(s) arecandidate TTI(s) in a special or partial subframe, and the size of thespecial bitmap can be determined based on the number of TTIs in thespecial or partial subframe.

In addition, as shown in FIG. 3, the eNB 300 according to the presentdisclosure may optionally include a CPU (Central Processing Unit) 310for executing related programs to process various data and controloperations of respective units in the eNB 300, a ROM (Read Only Memory)313 for storing various programs required for performing various processand control by the CPU 310, a RAM (Random Access Memory) 315 for storingintermediate data temporarily produced in the procedure of process andcontrol by the CPU 310, and/or a storage unit 317 for storing variousprograms, data and so on. The above circuitry 301, and transmitter 302,CPU 310, ROM 313, RAM 315 and/or storage unit 317 etc. may beinterconnected via data and/or command bus 320 and transfer signalsbetween one another.

Respective components as described above do not limit the scope of thepresent disclosure. According to one implementation of the disclosure,the functions of the above circuitry 301 and transmitter 302 may beimplemented by hardware, and the above CPU 310, ROM 313, RAM 315 and/orstorage unit 317 may not be necessary. Alternatively, the functions ofthe above circuitry 301 and transmitter 302 may also be implemented byfunctional software in combination with the above CPU 310, ROM 313, RAM315 and/or storage unit 317 etc.

FIG. 4 illustrates a flowchart of a wireless communication method 400performed by an eNB (e.g. the eNB 300) according to an embodiment of thepresent disclosure. The wireless communication method 400 can comprise astep 401 of generating a bitmap indicating candidate TTI(s) for aphysical channel in a subframe, a step 402 of transmitting the bitmap inthe RRC or MAC layer to a UE, and a step 403 of transmitting thephysical channel in one or more of the candidate TTI(s) to the UE. EachTTI in the subframe comprises 1-7 OFDM symbols, and the size of thebitmap depends on the lengths of TTIs in the subframe. The details andbenefits described in the above for eNB 300 can also be applied to thewireless communication method 400.

Accordingly, embodiments of the present disclosure also provide a UE anda wireless communication method performed by the UE.

FIG. 5 schematically illustrates a block diagram of a UE 500 accordingto an embodiment of the present disclosure. The UE 500 can comprise: areceiver 501 operative to receive a bitmap indicating candidate TTI(s)for a physical channel in a subframe in the RRC or MAC layer; andcircuitry 502 operative to determine the candidate TTI(s) based on thebitmap, wherein the receiver is also operative to receive the physicalchannel in one or more of the candidate TTI(s) by blindly decoding thecandidate TTI(s), and each TTI in the subframe comprises 1-7 orthogonalfrequency division multiplexing (OFDM) symbols, and the size of thebitmap depends on the lengths of TTIs in the subframe. In theembodiment, the UE 500 can obtain the information on the candidateTTI(s) based on the bitmap, and thus can only blindly decode thecandidate TTI(s) to receive the physical channel transmitted in one ormore of the candidate TTI(s).

The UE 500 according to the present disclosure may optionally include aCPU (Central Processing Unit) 510 for executing related programs toprocess various data and control operations of respective units in theUE 500, a ROM (Read Only Memory) 513 for storing various programsrequired for performing various process and control by the CPU 510, aRAM (Random Access Memory) 515 for storing intermediate data temporarilyproduced in the procedure of process and control by the CPU 510, and/ora storage unit 517 for storing various programs, data and so on. Theabove receiver 501, circuitry 502, CPU 510, ROM 513, RAM 515 and/orstorage unit 517 etc. may be interconnected via data and/or command bus520 and transfer signals between one another.

Respective components as described above do not limit the scope of thepresent disclosure. According to one implementation of the disclosure,the functions of the above receiver 501 and circuitry 502 may beimplemented by hardware, and the above CPU 510, ROM 513, RAM 515 and/orstorage unit 517 may not be necessary. Alternatively, the functions ofthe above receiver 501 and circuitry 502 may also be implemented byfunctional software in combination with the above CPU 510, ROM 513, RAM515 and/or storage unit 517 etc.

FIG. 6 illustrates a flowchart of a wireless communication method 600performed by a UE (e.g., the UE 500) according to an embodiment of thepresent disclosure. The wireless communication method 600 can comprise astep 601 of receiving a bitmap indicating candidate TTI(s) for aphysical channel in a subframe in the RRC or MAC layer, a step 602 ofdetermining the candidate TTI(s) based on the bitmap, and a step 603 ofreceiving the physical channel in one or more of the candidate TTI(s) byblindly decoding the candidate TTI(s), wherein each TTI in the subframecomprises 1-7 OFDM symbols, and the size of the bitmap depends on thelengths of TTIs in the subframe.

It is noted that the details and benefits described in the above for theeNB side can also be applied to the UE side, unless the contextindicates otherwise.

In another embodiment of the present disclosure, in order to determinecandidate TTI(s) for transmitting a physical channel in a subframe,valid TTI(s) for the physical channel are determined based on RE numberof each TTI in the subframe. The “valid TTI” for a physical channelherein refers to a TTI capable of transmitting the physical channel. Forexample, in the case that one TTI transmits one physical channel, if theRE number of the TTI is enough to transmit the physical channel, the TTIis a valid TTI. When it is configured that one physical channel can betransmitted in multiple TTIs, if the total RE number of the multipleTTIs is enough to transmit the physical channel, the multiple TTIs arevalid TTIs. Since the physical channel is only possible to betransmitted in the valid TTI(s), the UE only needs to at most blindlydecode the valid TTI(s) to receive the physical channel. In one example,all the valid TTI(s) are all taken as candidate TTI(s) for transmittingthe physical channel, and there is no bitmap to further indicatecandidate TTI(s); therefore, the UE needs to blindly decode all thevalid TTI(s). In another example, there is a bitmap applied to the validTTI(s) to further indicate which TTI(s) among the valid TTI(s) iscandidate TTI(s) for the physical channel. In either example, thesignaling overhead can be reduced. Particularly, for the latter example,since the bitmap can be only applied to the valid TTI(s) rather than allthe TTIs in a subframe, its size can be reduced.

Based on the above concept of determining valid TTIs based on the REnumber of each TTI in a subframe, an embodiment of the presentdisclosure provides a UE 700 as shown in FIG. 7 which schematicallyillustrates a block diagram of the UE 700 according to an embodiment ofthe present disclosure. The UE 700 can comprise: circuitry 701 operativeto determine valid TTI(s) for a physical channel in a subframe based onthe RE number of each TTI in the subframe; and a receiver 702 operativeto receive the physical channel in one or more of the valid TTI(s) byblindly decoding part or all of the valid TTI(s), wherein each TTIcomprises 1-7 OFDM symbols. In the embodiment, the UE can obtain theinformation on valid TTI(s) based on the RE number of each TTI, and thusonly need to blindly decode at most the valid TTI(s) rather than all theTTIs in the subframe. It is noted that the above descriptions on FIG. 5can be applicable to the UE 700 in FIG. 7 unless the context indicatesotherwise.

Considering EPDCCH as the physical channel, reference signalconfiguration (for example CSI-RS dropping behavior, periodicity, CRSport number and PDCCH configuration) and MBSFN configuration will impactthe RE number in a TTI for transmitting the EPDCCH. As an example, thefollowing assumptions can be made.

-   -   DCI size is 32 bits (including CRC), and QPSK and ⅓ coding rate        are adopted, so the required RE number to transmit such a DCI is        32×3/2=48.    -   4 PRBs are allocated for a shortened TTI in a subframe and the        TTI length is 1 OFDM symbol.    -   Reference signal assumption is as shown in FIG. 8 which        schematically illustrates reference signal assumption in an        example. In FIG. 9, two CRS ports, 24 DMRS REs, 8 port CSI-RS        and one OFDM symbol PDCCH are assumed in a PRB. In OFDM symbol        (or TTI) 0, as PDCCH occupies the whole PRB, available RE number        for EPDCCH is zero. In OFDM symbol (or TTI) 5, 6, 12 and 13, as        DMRS RE number in a PRB is 6, available RE number for EPDCCH        is 6. Other OFDM symbols' available RE number can be calculated        in similar ways.

Based on above assumptions, the RE number in each TTI of one subframecan be determined as shown in Table 1. Since the required RE number fortransmitting the above DCI is 48, only TTIs (or OFDM symbols) 1, 2, 3and 8 are valid for EPDCCH.

TABLE 1 Number of PRB number Total RE Valid or not TTI REs per PRB infrequency number for EPDCCH 0 0 4 0 N 1 12 4 48 Valid 2 12 4 48 Valid 312 4 48 Valid 4 8 4 32 N 5 6 4 24 N 6 6 4 24 N 7 8 4 32 N 8 12 4 48Valid 9 8 4 32 N 10 8 4 32 N 11 8 4 32 N 12 6 4 24 N 13 6 4 24 N

In one embodiment, all the valid TTI(s) are taken as candidate TTI(s),and the UE 700 will blindly decode all the valid TTI(s). In the aboveexample shown in Table 1, the four valid TTIs can be taken as candidateTTIs for EPDCCH.

Alternatively, in another embodiment, a bitmap applied to the validTTI(s) can be send from the eNB to further indicate which TTI(s) amongthe valid TTI(s) is candidate TTI(s) for the physical channel.Accordingly, the receiver 702 can be further operative to receive abitmap in the RRC or MAC layer indicating candidate TTI(s) for thephysical channel among the valid TTI(s); the one or more of the validTTI(s) for transmitting the physical channel is among the candidateTTI(s), and the receiver 702 can be operative to blindly decode thecandidate TTI(s) when receiving the physical channel. Here, the size ofthe bitmap can be equal to the number of the valid TTI(s) in thesubframe since the bitmap can be only applied to the valid TTI(s), soits size can be smaller than a bitmap applied to all the TTIs in thesubframe. For the above example shown in Table 1, a 4 bit bitmap can beused to indicate which TTI(s) in the four valid TTIs are candidateTTI(s) for the EPDCCH. Alternatively, the size of the bitmap can beequal to the largest one of the numbers of valid TTI(s) in respectivesubframes available to the UE. There are different types of subframes,for example, MBSFN (Multicast Broadcast Single Frequency Network)subframe and non-MBSFN subframe, and some RSs like CSI-RS may not existin every subframe. Therefore, different types of subframes can havedifferent situations on valid TTI number. For the example shown in FIG.8, the CSI-RS may not exist in some subframes, so the TTIs (OFDMsymbols) 9 and 10 may be valid TTIs for the EPDCCH in some subframes.Therefore, in order to use the same bitmap for different types ofsubframes (for example, the one shown in FIG. 7 with CSI-RS in OFDMsymbols 9 and 10, and the one without CSI-RS in OFDM symbols 9 and 10),the size of the bitmap can be the largest size suitable for all types ofsubframes, that is, be equal to the largest one of the numbers of validTTI(s) in respective subframes available to the UE. In the above exampleshown in FIG. 8 and Table 1, a 6 bit bitmap can be used to indicatesymbols (TTIs) 1, 2, 3, 8, 9 and 10. For a subframe with CSI-RS, thebits in the bitmap for symbols 9 and 10 are not valid.

Usually, one physical channel is only transmitted in one TTI. However,sometimes, too few valid TTIs may exist in a subframe if one physicalchannel is only transmitted in one TTI. Therefore, as proposed in thepresent disclosure, multiple TTIs can be used to transmit one physicalchannel such as EPDCCH. In the case that the RE number of eachindividual TTI of a set of TTIs in a subframe is not enough to transmitthe physical channel, if the total RE number of the set of TTIs isenough to transmit the physical channel, the set of TTIs can bedetermined as valid, the set of TTIs in combination are used to transmitthe physical channel, and the receiver 702 can jointly decode the set ofTTIs. For example, assuming two consecutive TTIs can transmit oneEPDCCH, in the example shown in FIG. 8 and Table 1, among the invalidTTIs 0, 4, 5, 6, 7, 9, 10, 11, 12 and 13 when the EPDCCH can only betransmitted in one TTI, the combinations of TTIs 4 and 5, 6 and 7, and 9and 10 can also be determined as valid since each of the combinationshas more than 48 REs, as shown in Table 2. This can increase thecapacity of shortened TTI transmission. In an embodiment, the EPDCCHover two TTIs can only be transmitted in TTIs which are invalid when theEPDCCH is only transmitted in one TTI.

TABLE 2 Number PRB Valid for Valid for of REs number in Total RE 1 TTI 2TTI TTI per PRB frequency number transmission transmission 0 0 4 0 N 112 4 48 Valid 2 12 4 48 Valid 3 12 4 48 Valid 4 8 4 32 N Valid 5 6 4 24N 6 6 4 24 N Valid 7 8 4 32 N 8 12 4 48 Valid 9 8 4 32 N Valid 10 8 4 32N 11 8 4 32 N Valid 12 6 4 24 N 13 6 4 24 N

In an embodiment of the present disclosure, there is also provided awireless communication method 900 performed by the above UE 700. FIG. 9illustrates a flowchart of a wireless communication method 900 performedby a UE according to an embodiment of the present disclosure. Thewireless communication 900 can comprise: a step 901 of determining validTTI(s) for a physical channel in a subframe based on the RE number ofeach TTI in the subframe; and a step 902 of receiving the physicalchannel in one or more of the valid TTI(s) by blindly decoding part orall of the valid TTI(s), wherein each TTI comprises 1-7 OFDM symbols.The details and benefits described for the above UE 700 can also beapplied to the wireless communication method 900.

At the eNB side, embodiments of the present disclosure provide an eNBand a wireless communication method performed by the eNB.

FIG. 10 illustrates a flowchart of a wireless communication method 1000performed by an eNB according to an embodiment of the presentdisclosure. The wireless communication method 1000 can comprise a step1001 of determining valid TTI(s) for a physical channel in a subframebased on the RE number of each TTI in the subframe; and a step 1002 oftransmitting the physical channel in one or more of the valid TTI(s) toa UE, wherein each TTI comprises 1-7 OFDM symbols. Optionally, themethod 1000 can also comprise transmitting a bitmap in the RRC or MAClayer indicating candidate TTI(s) for the physical channel among thevalid TTI(s) to the UE, wherein the size of the bitmap is equal to thenumber of the valid TTI(s) in the subframe or the largest one of thenumbers of valid TTI(s) in respective subframes available to the UE, andthe one or more of the valid TTI(s) for transmitting the physicalchannel is among the candidate TTI(s).

An embodiment of the present disclosure also provides an eNB forperforming the above method 1000, which can comprise: circuitryoperative to determine valid TTI(s) for a physical channel in a subframebased on the RE number of each TTI in the subframe; and a transmitteroperative to transmit the physical channel in one or more of the validTTI(s) to a UE, wherein each TTI comprises 1-7 OFDM symbols. Optionally,the transmitter can be further operative to transmit a bitmap in the RRCor MAC layer indicating candidate TTI(s) for the physical channel amongthe valid TTI(s) to a UE, wherein the size of the bitmap is equal to thenumber of the valid TTI(s) in the subframe or the largest one of thenumbers of valid TTI(s) in respective subframes available to the UE,wherein the one or more of the valid TTI(s) for transmitting thephysical channel is among the candidate TTI(s). The block diagram of theeNB in this embodiment can refer to the structure shown in FIG. 3.

It is noted that the details and benefits described in the above for theUE side can also be applied to the eNB side, unless the contextindicates otherwise.

The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be realized by an LSIas an integrated circuit, and each process described in the eachembodiment may be controlled by LSI. They may be individually formed aschips, or one chip may be formed so as to include a part or all of thefunctional blocks. They may include a data input and output coupledthereto. The LSI here may be referred to as an IC, a system LSI, a superLSI, or an ultra LSI depending on a difference in the degree ofintegration. However, the technique of implementing an integratedcircuit is not limited to the LSI and may be realized by using adedicated circuit or a general-purpose processor. In addition, a FPGA(Field Programmable Gate Array) that can be programmed after themanufacture of the LSI or a reconfigurable processor in which theconnections and the settings of circuits cells disposed inside the LSIcan be reconfigured may be used.

It is noted that the present disclosure intends to be variously changedor modified by those skilled in the art based on the descriptionpresented in the specification and known technologies without departingfrom the content and the scope of the present disclosure, and suchchanges and applications fall within the scope that claimed to beprotected. Furthermore, in a range not departing from the content of thedisclosure, the constituent elements of the above-described embodimentsmay be arbitrarily combined.

Embodiments of the present disclosure can at least provide the followingsubject matters.

1. A user equipment (UE) comprising:

circuitry operative to determine valid transmission time interval(s)(TTI(s)) for a physical channel in a subframe based on the resourceelement (RE) number of each TTI in the subframe; and

a receiver operative to receive the physical channel in one or more ofthe valid TTI(s) by blindly decoding part or all of the valid TTI(s),

wherein each TTI comprises 1-7 orthogonal frequency divisionmultiplexing (OFDM) symbols.

2. The user equipment according to 1, wherein

the receiver is further operative to receive a bitmap in the radioresource control (RRC) or medium access control (MAC) layer indicatingcandidate TTI(s) for the physical channel among the valid TTI(s),wherein the size of the bitmap is equal to the number of the validTTI(s) in the subframe or the largest one of the numbers of valid TTI(s)in respective subframes available to the UE; and

the one or more of the valid TTI(s) for transmitting the physicalchannel is among the candidate TTI(s), and the receiver is operative toblindly decode the candidate TTI(s) when receiving the physical channel.

3. The user equipment according to 2, wherein

the same bitmap is used for different types of subframes, and

the size of the bitmap is equal to the largest one of the numbers ofvalid TTI(s) in respective subframes available to the UE.

4. The user equipment according to 1, wherein

the receiver is operative to blindly decode all the valid TTI(s) whenreceiving the physical channel.

5. The user equipment according to 1, wherein

the circuitry is further operative to determine that a set of TTIs inthe subframe are valid TTIs if the total RE number of the set of TTIs isenough to transmit the physical channel in the case that the RE numberof each individual TTI of the set of TTIs is not enough to transmit thephysical channel, wherein the set of TTIs in combination are used totransmit the physical channel.

6. An eNode B (eNB) comprising:

circuitry operative to determine valid transmission time interval(s)(TTI(s)) for a physical channel in a subframe based on the resourceelement (RE) number of each TTI in the subframe; and

a transmitter operative to transmit the physical channel in one or moreof the valid TTI(s) to a user equipment (UE),

wherein each TTI comprises 1-7 orthogonal frequency divisionmultiplexing (OFDM) symbols.

7. The eNode B according to 6, wherein

the transmitter is further operative to transmit a bitmap in the radioresource control (RRC) or medium access control (MAC) layer indicatingcandidate TTI(s) for the physical channel among the valid TTI(s) to theUE, wherein the size of the bitmap is equal to the number of the validTTI(s) in the subframe or the largest one of the numbers of valid TTI(s)in respective subframes available to the UE, and

the one or more of the valid TTI(s) for transmitting the physicalchannel is among the candidate TTI(s).

8. The eNode B according to 7, wherein

the same bitmap is used for different types of subframes, and

the size of the bitmap is equal to the largest one of the numbers ofvalid TTI(s) in respective subframes available to the UE.

9. The eNode B according to 6, wherein

the transmitter is operative to transmit the physical channel in one ormore of the valid TTI(s) by taking all the valid TTI(s) as candidateTTI(s) for the physical channel.

10. The eNode B according to 6, wherein

the circuitry is further operative to determine that a set of TTIs inthe subframe are valid TTIs if the total RE number of the set of TTIs isenough to transmit the physical channel in the case that the RE numberof each individual TTI of the set of TTIs is not enough to transmit thephysical channel, wherein the set of TTIs in combination are used totransmit the physical channel.

11. An eNode B (eNB) comprising:

circuitry operative to generate a bitmap indicating candidatetransmission time interval(s) (TTI(s)) for a physical channel in asubframe; and

a transmitter operative to transmit the bitmap in the radio resourcecontrol (RRC) or medium access control (MAC) layer, and transmit thephysical channel in one or more of the candidate TTI(s),

wherein each TTI in the subframe comprises 1-7 orthogonal frequencydivision multiplexing (OFDM) symbols, and the size of the bitmap dependson the lengths of TTIs in the subframe.

12. The eNode B according to 11, wherein

the lengths of the TTIs in the subframe are user equipment(UE)-specific.

13. The eNode B according to 12, wherein

the lengths of the TTIs in the subframe depend on UE's coveragesituation.

14. The eNode B according to 11, wherein

the lengths of the TTIs in the subframe are all the same; and

if the lengths of the TTIs are not an exact divider of 14, at least twoTTIs in the subframe are arranged to overlap each other, or some OFDMsymbols in the subframe are not assigned to the TTIs.

15. The eNode B according to 11, wherein

If the subframe is a special or partial subframe, n bits of the bitmapare applied to indicate the candidate TTI(s), and n depends on thenumber of TTIs in the special or partial subframe.

16. A user equipment (UE) comprising:

a receiver operative to receive a bitmap indicating candidatetransmission time interval(s) (TTI(s)) for a physical channel in asubframe in the radio resource control (RRC) or medium access control(MAC) layer; and

circuitry operative to determine the candidate TTI(s) based on thebitmap,

wherein the receiver is also operative to receive the physical channelin one or more of the candidate TTI(s) by blindly decoding the candidateTTI(s), and

each TTI in the subframe comprises 1-7 orthogonal frequency divisionmultiplexing (OFDM) symbols, and the size of the bitmap depends on thelengths of TTIs in the subframe.

17. The user equipment according to 16, wherein

the lengths of the TTIs in the subframe are user equipment(UE)-specific.

18. The user equipment according to 17, wherein

the lengths of the TTIs in the subframe depend on UE's coveragesituation.

19. The user equipment according to 16, wherein

the lengths of the TTIs in the subframe are all the same; and

if the lengths of the TTIs are not an exact divider of 14, at least twoTTIs in the subframe are arranged to overlap each other, or some OFDMsymbols in the subframe are not assigned to the TTIs.

20. The user equipment according to 16, wherein

If the subframe is a special or partial subframe, n bits of the bitmapare applied to indicate the candidate TTI(s), and n depends on thenumber of TTIs in the special or partial subframe.

21. A wireless communication method performed by a user equipment (UE)comprising:

determining valid transmission time interval(s) (TTI(s)) for a physicalchannel in a subframe based on the resource element (RE) number of eachTTI in the subframe; and

receiving the physical channel in one or more of the valid TTI(s) byblindly decoding part or all of the valid TTI(s),

wherein each TTI comprises 1-7 orthogonal frequency divisionmultiplexing (OFDM) symbols.

22. The wireless communication method according to 21, furthercomprising:

receiving a bitmap in the radio resource control (RRC) or medium accesscontrol (MAC) layer indicating candidate TTI(s) for the physical channelamong the valid TTI(s),

wherein the size of the bitmap is equal to the number of the validTTI(s) in the subframe or the largest one of the numbers of valid TTI(s)in respective subframes available to the UE; and

the one or more of the valid TTI(s) for transmitting the physicalchannel is among the candidate TTI(s), and the candidate TTI(s) areblindly decoded when receiving the physical channel.

23. The wireless communication method according to 22, wherein

the same bitmap is used for different types of subframes, and

the size of the bitmap is equal to the largest one of the numbers ofvalid TTI(s) in respective subframes available to the UE.

24. The wireless communication method according to 21, wherein

all the valid TTI(s) are blindly decoded when receiving the physicalchannel.

25. The wireless communication method according to 21, furthercomprising:

determining that a set of TTIs in the subframe are valid TTIs if thetotal RE number of the set of TTIs is enough to transmit the physicalchannel in the case that the RE number of each individual TTI of the setof TTIs is not enough to transmit the physical channel, wherein the setof TTIs in combination are used to transmit the physical channel.

26. A wireless communication method performed by an eNode B (eNB),comprising:

determining valid transmission time interval(s) (TTI(s)) for a physicalchannel in a subframe based on the resource element (RE) number of eachTTI in the subframe; and

transmitting the physical channel in one or more of the valid TTI(s) toa user equipment (UE),

wherein each TTI comprises 1-7 orthogonal frequency divisionmultiplexing (OFDM) symbols.

27. The wireless communication method according to 26, furthercomprising:

transmitting a bitmap in the radio resource control (RRC) or mediumaccess control (MAC) layer indicating candidate TTI(s) for the physicalchannel among the valid TTI(s) to the UE, wherein

the size of the bitmap is equal to the number of the valid TTI(s) in thesubframe or the largest one of the numbers of valid TTI(s) in respectivesubframes available to the UE, and

the one or more of the valid TTI(s) for transmitting the physicalchannel is among the candidate TTI(s).

28. The wireless communication method according to 27, wherein

the same bitmap is used for different types of subframes, and

the size of the bitmap is equal to the largest one of the numbers ofvalid TTI(s) in respective subframes available to the UE.

29. The wireless communication method according to 26, wherein

the physical channel is transmitted in one or more of the valid TTI(s)by taking all the valid TTI(s) as candidate TTI(s) for the physicalchannel.

30. The wireless communication method according to 26, furthercomprising:

determining that a set of TTIs in the subframe are valid TTIs if thetotal RE number of the set of TTIs is enough to transmit the physicalchannel in the case that the RE number of each individual TTI of the setof TTIs is not enough to transmit the physical channel, wherein the setof TTIs in combination are used to transmit the physical channel.

31. A wireless communication method performed by an eNode B (eNB)comprising:

generating a bitmap indicating candidate transmission time interval(s)(TTI(s)) for a physical channel in a subframe;

transmitting the bitmap in the radio resource control (RRC) or mediumaccess control (MAC) layer;

transmitting the physical channel in one or more of the candidateTTI(s),

wherein each TTI in the subframe comprises 1-7 orthogonal frequencydivision multiplexing (OFDM) symbols, and the size of the bitmap dependson the lengths of TTIs in the subframe.

32. The wireless communication method according to 31, wherein

the lengths of the TTIs in the subframe are user equipment(UE)-specific.

33. The wireless communication method according to 32, wherein

the lengths of the TTIs in the subframe depend on UE's coveragesituation.

34. The wireless communication method according to 31, wherein

the lengths of the TTIs in the subframe are all the same; and

if the lengths of the TTIs are not an exact divider of 14, at least twoTTIs in the subframe are arranged to overlap each other, or some OFDMsymbols in the subframe are not assigned to the TTIs.

35. The wireless communication method according to 31, wherein

If the subframe is a special or partial subframe, n bits of the bitmapare applied to indicate the candidate TTI(s), and n depends on thenumber of TTIs in the special or partial subframe.

36. A wireless communication method performed by a user equipment (UE)comprising:

receiving a bitmap indicating candidate transmission time interval(s)(TTI(s)) for a physical channel in a subframe in the radio resourcecontrol (RRC) or medium access control (MAC) layer;

determining the candidate TTI(s) based on the bitmap; and

receiving the physical channel in one or more of the candidate TTI(s) byblindly decoding the candidate TTI(s),

wherein each TTI in the subframe comprises 1-7 orthogonal frequencydivision multiplexing (OFDM) symbols, and the size of the bitmap dependson the lengths of TTIs in the subframe.

37. The wireless communication method according to 36, wherein

the lengths of the TTIs in the subframe are user equipment(UE)-specific.

38. The wireless communication method according to 37, wherein

the lengths of the TTIs in the subframe depend on UE's coveragesituation.

39. The wireless communication method according to 36, wherein

the lengths of the TTIs in the subframe are all the same; and

if the lengths of the TTIs are not an exact divider of 14, at least twoTTIs in the subframe are arranged to overlap each other, or some OFDMsymbols in the subframe are not assigned to the TTIs.

40. The wireless communication method according to 36, wherein

If the subframe is a special or partial subframe, n bits of the bitmapare applied to indicate the candidate TTI(s), and n depends on thenumber of TTIs in the special or partial subframe.

In addition, embodiments of the present disclosure can also provide anintegrated circuit which comprises module(s) for performing the step(s)in the above respective communication methods. Further, embodiments ofthe present can also provide a computer readable storage medium havingstored thereon a computer program containing a program code which, whenexecuted on a computing device, performs the step(s) of the aboverespective communication methods.

1. A user equipment comprising: a receiver, which, in operation,receives a bitmap indicating a candidate of transmission time interval(TTI), which is one or more symbols used for a physical channel among 14symbols; and circuitry, which, in operation, blindly decodes thephysical channel in the candidate based on the bitmap.
 2. The userequipment according to claim 1, wherein a length of the TTI is variable,and a size of the bitmap is constant for all of different lengths of theTTI.
 3. The user equipment according to claim 1, wherein a size of thebitmap is equal to the largest one of numbers of the candidateconfigurable in the 14 symbols.
 4. The user equipment according to claim1, wherein a size of the bitmap is 14 bits.
 5. The user equipmentaccording to claim 1, wherein the receiver, in operation, receives thebitmap in a radio resource control (RRC) or a medium access control(MAC).
 6. The user equipment according to claim 1, wherein a length ofthe TTI is specific to the user equipment.
 7. The user equipmentaccording to claim 1, wherein a length of the TTI depends on coverage ofthe user equipment.
 8. The user equipment according to claim 1, whereinthe candidate of the TTI is based on a configuration of referencesignal.
 9. A receiving method comprising: receiving a bitmap indicatinga candidate of transmission time interval (TTI), which is one or moresymbols used for a physical channel among 14 symbols; and blindlydecoding the physical channel in the candidate based on the bitmap.